I disagree. I believe in this context (always difficult to know I appreciate)the meanings are very different. Obviously the second sentence as you say " Usted tendra que dormir esta noche" means, You will have to sleep tonight.

On the other hand "Debera dormir esta noche" can not automatically be substituted for You will have to sleep tonight, because it means You SHOULD/MUST sleep tonight and they have a different meaning"

We can use future tenses to make PREDICTIONS or ASSUMPTIONS. As I believe is the case here. Eg. " I've been working non stop for twelve hours, I'm exhausted" to which his wife replies, "You SHOULD sleep well tonight" Or, " I have an exam on Wednesday, I'm a bit worried" a friend replies, "You've studied loads, you SHOULD pass no problem" At a bus stop, " Do you think it will be on time?" " It SHOULD BE, I get it every day and its never normally late" etc etc. Again if you insist its possible to use, Must, Ought to, Have (has) to in these examples, " You MUST sleep well tonight", "You OUGHT TO pass the exam" " It has to be on time, its never late"

It also isn't though simply an argument as to how synonymous Must, should, ought to, have to are etc. Yes they can often be interchanged for one another to convey the same meaning with different senses of obligation or politeness etc. However just as we have different words so do they in Spanish. So if it asks you to say HE HAS TO use Tener, if they ask you to say Should, use Deber etc. Why over complicate things with every possible synonym or similar phrase? When you speak in your own time use whatever you prefer!! However if they ask you to translate a specific word then why not just do it?. It's possible to say " I am going to prevent the flow of electricity to the illumination, but I'd probably just say, " I'm going to turn out the light"

Anyway just my thoughts, but I think that sometimes we should think more about how we use our own language before trying to learn or even worse change ( to fit our needs) another one.

Well, judging from the fact that a few minutes ago I ran into this one: "Él deberá encontrar su pasión en la vida." and they accepted "He shall find his passion in life.", I would think deberá meaning "shall" would also be acceptable in this case.

@ "frank479" Yes, "shall" is accepted but you have to say the sentence like this: "You shall have to sleep tonight." (It sounds a little old English but that's how Duolingo accepts the sentence with "shall").

What is the difference in English between "you need to sleep tonight" and "you will need to sleep tonight." They seem to mean the same thing to me with a slight emphasis difference in how you view the time frame. I expect it is the same for the Spanish.

In addition adding 'will' shifts when the 'needing' will happen. 'You need...' is now, whereas 'You will need ...' is later, but not necessary now. Imagine you're talking to some one who is about to do some exhausting work - 'will need to sleep', as opposed to someone who already has - 'need to sleep'.

namayani is mostly right: "debes" it's either a command ("you have to sleep tonight") or a suggestion ("you ought to sleep tonight") when you talk about future things, while "deberás" is an order to be complied in the future ("you will sleep tonight" or "you must sleep tonight") just like "debes" is an order to be complied in the present ("debes dormir ahora ")

I'm not entirely convinced. I don't think using the present tense to refer to future events is grammatically sound in English and I suspect the same would be true in Spanish. One of your points was that the tense indicates at what time a command would be but this is missing the point because regardless of whether you use present or future tense, the time when the command is enacted will be 'tonight' which is in the future. You can't comply with an order in the present if the order refers to future events.

If the event is in the future then only the future tense should be used. As to the strength of the obligation, we know in the present tense deber can range in meaning from ought to to must so I see no reason why the same shouldn't apply in the future, I find it difficult to accept that future tense would imply a lesser degree of obligation or vice versa.

same here. what I'm thinking is this
Scenario A: We're talking and you seem really tired and I feel that now the things are such that you must sleep tonight and I say "Debes dormir esta noche."
Scenario B: You have a habit of not sleeping at night, but tomorrow we have to do something important so tonight you really must sleep because tomorrow things will be such that it will have been better if you had slept so I say "Deberás dormir esta noche."
Or am I not getting this right at all? I googled to learn more about 'deberás' and it provided senteces such as "Si haces lo que no debes, deberás sufrir lo que no mereces" B. Franklin(?) which would imply that "debes" has a connotation of something you must do in general, while 'deberás' is something you have to or only might have to do in the future.

I think there's a simple answer to this overlooked by the other commenters so far. Esta noche is a future event so the future tense should be used in both languages. Therefore I believe that in correct grammar "Debes dormir esta noche" and "You must sleep tonight" are both wrong. The reason I think the main accepted answer uses "must" is because I think it may actually be a conditional form, otherwise it would sound wrong to our ears.

I've read all the answers, but still not satisfied. I think the context matters in this case, because i've read the sentence in a different way: there's a kid that didn't went to bed yesterday, his friends are sleeping over later during the week and tomorrow there's a difficult test in school. So, he must sleep THIS night. I'm sure it is common to say tonight, but can somebody with enough knowledge and experience tell me that 'this night' is against one possible grammatical rule in written or spoken english? The sentences that can be translated alternatively on duolingo are plethora. Cheers. (PS Give us a break. And i want my point back!)

Who says "this night" in place or "tonight" in English? That sounds very awkward. It is the literally translation but not how English-speaking people would say it. "I'm going to the game this night." No one would ever say that.

It obviously does matter if you are a native speaker or not, no matter where you are from. English is English. As long as we aren't talking about slang, it's the same language. The language works the same. And 'this night' is obviously fine to say, and actually preferable in some situations, like the Jewish thing, or when the structure of a sentence allows for it ('this' being a modifier of the noun 'night') as opposed to a sentence which looks just for a noun (tonight).

Only 'tonight':
What are you doing tonight?

Only 'this night':
On this night one year ago my cow jumped over the moon

I disagree. I am a native speaker of English and no one would EVER say "this night" in place of "tonight" in my country. Perhaps it's used in another English-speaking country. In what English-speaking country have you heard this usage? Yes, someone would understand your meaning but it's not how it's said.

No offense to those who claim to be native speakers each time but it doesn't matter, because language varies regionally so much, that your individual experiences are practically meaningless, unless you will claim to have lived all over US, Britain, New Zealand, Australia, Israel, etc where English is spoken in its various dialects. 'This night' is certainly less common than 'tonight' ...but it's still perfectly correct and could be used for emphasis...."what is so special about this night of all nights?" ....again please refrain from using 'call to authority fallacy', at most you could say that "I am from New York and I am a native speaker, and where I live, that's a rarely or never used turn of phrase.....

I believe you if you say you would never express yourself this way. Certainly in the US and Britain this is a normal, though less common, way of saying that. In the US at a bar it might elicit "Waz widda 'this night' jazz? shaddup 'n' have a beer"

yes, native speaker from the US and a former English teacher. If someone said "I will go to the game this night" I would pick up on that as unusual, perhaps someone putting on airs (frontin') or being melodramatic but not wrong or unheard of.

I really don't mean to be argumentative, but I am from the United States, and yes, I would never express myself using "this night" in place of "tonight" in the context above. But neither would anyone else here. I have never heard anyone say "this night" here, and if I did, I would certainly take notice as it is never heard. And it's not a matter of colloquial vs. formal speech. If I may ask, are you a native English speaker and where are you from?

Yes, it seems that saying things like "must" with sleep just don't work. If someone tells me I "must" sleep, I probably won't be able to, but "ought to" is a much better translation. Besides "must" is better with tener que

I translated it as 'you have to sleep tonight' and was marked wrong. It said I missed the word 'will'. Ehhh.. I dunno. 'have to' and 'must' are pretty much synonyms so if you need will with one you need it with the other, otherwise it's implied with both. Soo... yeah. I hate you Duolingo. Nah, just kidding. I love you.

I can't believe that I put a double negative in there; this must have been triggered by the fact that not only was I not feeling well when I wrote this, but also because I wrote it in a great rush, being busy with many other tasks. In any event, once I saw your comment, I quickly corrected that embarrassing error that I had made.

Thanks for your answer; even though -- to me, at least -- "must," "have to" and "need to" are essentially equivalent expressions in English, I understand the logic contained within the corresponding Spanish structures. For that, I'd like to thank you for taking the time to provide me with a sound, well-reasoned, correct and clear answer. :-)

Hello AriW1977, Hahaha! That can happen to anyone, no problem, but you're right, I'm a native English speaker and it causes me far too confusion when not being always able to differentiate them completely "Deber = Tener que = Need to/ Must/ have to", I always said that there is no difference between of them, but when I moved into Colombia, People prefers to choose them according to every situation but it's very very different, unlike as I was taught in USA, in Colombia they told me this "Must = Debe - it's an obligation which is demanded by your parents, boss(es), or someone far above you in a range of something either at work, at school, in college" / "Have to" - It's a prohibition at a time of doing something, but everything is mainly in your hands, since if you want, you do it, so you have to make up your mind" - and "Need to = tengo que", but as a minor obligation or something more as a suggestion (the same as "Should/ought to")", ok, anyways, as you are saying they're equivalent sentences.

A particular case is: "I will go to = I'm going to go = Iré a / voy a", they're also equivalent sentences to me, due to it comes to translating the future in English is something very similar though, but I think that Duo doesn't want that we mix the meanings for keeping the fixed grammar. -I removed the suggestion because I don't like to do in public!

The problem I have with that, Christian is that "must" isn't future tense so it's incorrect to suggest that "deberá" could ever simply translate as "must". I believe this exercise may be grammatically incorrect.

The complication is that "must" used to be the inflected form of the verb (like "could" for "can", "should" for "shall", etc), while these days "must" is generally synonymous with the present tense there are situations where it is used in inflected forms (possibly past, conditional or subjunctive). This is probably done unknowingly by the speaker but "must" doesn't always sound wrong when you use it in a another tense/aspect.

The point of that diversion is that I think "You must sleep tonight" is generally lazy English but the one situation where it could be correct is if the sentence is conditional - "You must sleep tonight" meaning "You would have to sleep tonight".

I'm repeating the question below bc I don't see an answer yet: What is the difference between:
"deberás dormir esta noche" and
"debes dormir esta noche"
is there any nuance between the two, or do they mean the same thing?

Well, “If you do what you shouldn't do, then you should suffer what you don't deserve”, but that’s a translation. So I went after the original quote. I never found it. But sure suffered a world of pop-up ads.

Can somebody explain why this sentence can be translated as "you will have to" and also as "you must" but not as "you have to?" Is there a difference between "you must" and "you have to?" I understand why it's future tense and "you will have to" is correct, but "you must" doesn't make a lot of sense to me...

I don't think they should've translated it as "you will have to"... Anyway, the difference between "you must" and "you have to" is the verb, Spanish has an equivalent for both. "Must" would use the verb "deber", while "to have to" would use "tener que".

That's terribly awkward sounding. "This night" might sound okay at the beginning of a sentence, and when used for dramatic effect, such as "This night will live on forever" or "This night will be the night we remember forever." Maybe in response to a question, "Which night, [points to day on calendar] that night?".... "No, this night." But putting "This night" at the end of a sentence sounds strange. We would say "tonight". Again, possibly for the purposes of dramatic effect, like if someone told someone who was working all night on something "You will have to sleep eventually." and that second person responded "I will sleep tomorrow night" and the first someone responded "No, you will have to sleep THIS night."

i can not see the difference between
- debes (debes que beber agua ) you should drink water
- debias ( debias beber water) you should drink water
- deberias ( deberias beber agua ) you should drink water

So what I think so far is that the present indicative of deber (debo, debes, deben, etc.) is used to mean "must," whereas (as I saw in the discussion from an earlier sentence), it means "should" when used in the conditional form of the verb. But now DL is bring in the future tense? so... does both conditional and future indicative mean "should," and if so, are they completely interchangeable? when do you use one over the other?

What the hell??! In what country does NOCHE mean EVENING?? I've always known the word, "noche" to mean, "night". I was 100% certain I had the translation correct. I was shocked when I read saw that red pop up telling me I'm wrong and why? Bc I translated noche into night. Doesn't anyone else have an issue with this?

"Noche" can mean "evening" or "night." The phrase "esta noche," although commonly understood to mean "tonight," can also mean "this evening." "Buenas noches" can be used as a greeting meaning "Good evening" or as a farewell meaning "Good night." http://www.spanishdict.com/translate/evening

Although the most common meaning for "noche" is night (and "está noche" usually means tonight), "noche" can also mean evening. The most familiar example of this is "Buenas noches" which can be used as a greeting meaning good evening and also as a farewell meaning good night. http://www.spanishdict.com/translate/noche

I wrote 'you have to sleep tonight' and was told it was wrong and should have been 'you will have to sleep tonight'. Quite frankly I don't see why my translation wasn't accepted. Surely there is no real difference between 'you must sleep' (the official translation given above), and 'you have to sleep'. Can someone please clarify this for me?

You are not going to belive this!
Uhh this is how it goes.
Alians are invading,
They took out the cell tower,
The citys on fire,
My car runs,but it has two flat tires,
We got a pizza problem.
I'm at a lose, no sause.
¡To be contined!